The present invention relates to an arrangement for decoding traffic information regional tone signals. The regional tone signals are contained in the form of a carrier which is amplitude-modulated therewith in a received broadcast signal which has already been demodulated in a conventional radio receiver.
In the journal "Funkschau", 1974, pages 535 to 538, the system currently used in Germany and other European countries for broadcasting traffic information to radio listeners is described. In this system, a territory is divided into several traffic information regions by adding regional tone signals to the traffic information signal. These regional tone signals, whose frequency, i.e., the regional tone frequency, is the information on the region, are low-frequency signals which are impressed on the carrier, having a frequency of 57 kHz in the known system, by amplitude modulation. They are derived from the carrier by integral frequency division.
This traffic information broadcasting system is described in detail in the journal "Rundfunktechnische Mitteilungen" 1974, pp. 193 to 202. According to this reference, system parameters were so chosen that the decoder circuits required for automatic traffic information reception were compatible with conventional analog-signal-processing receiver circuits and did not interfere therewith. The hitherto used decoder circuits are, therefor, analog circuits as well.